github.com/hugorut/terraform@v1.1.3/website/docs/language/functions/regex.mdx (about) 1 --- 2 page_title: regex - Functions - Configuration Language 3 description: |- 4 The regex function applies a regular expression to a string and returns the 5 matching substrings. 6 --- 7 8 # `regex` Function 9 10 `regex` applies a 11 [regular expression](https://en.wikipedia.org/wiki/Regular_expression) 12 to a string and returns the matching substrings. 13 14 ```hcl 15 regex(pattern, string) 16 ``` 17 18 The return type of `regex` depends on the capture groups, if any, in the 19 pattern: 20 21 - If the pattern has no capture groups at all, the result is a single string 22 covering the substring matched by the pattern as a whole. 23 - If the pattern has one or more _unnamed_ capture groups, the result is a 24 list of the captured substrings in the same order as the definition of 25 the capture groups. 26 - If the pattern has one or more _named_ capture groups, the result is a 27 map of the captured substrings, using the capture group names as map keys. 28 29 It's not valid to mix both named and unnamed capture groups in the same pattern. 30 31 If the given pattern does not match at all, the `regex` raises an error. To 32 _test_ whether a given pattern matches a string, use 33 [`regexall`](/language/functions/regexall) and test that the result has length greater than 34 zero. 35 36 The pattern is a string containing a mixture of literal characters and special 37 matching operators as described in the following table. Note that when giving a 38 regular expression pattern as a literal quoted string in the Terraform 39 language, the quoted string itself already uses backslash `\` as an escape 40 character for the string, so any backslashes intended to be recognized as part 41 of the pattern must be escaped as `\\`. 42 43 | Sequence | Matches | 44 | ---------------------- | -------------------------------------------------------------------------------- | 45 | `.` | Any character except newline | 46 | `[xyz]` | Any character listed between the brackets (`x`, `y`, and `z` in this example) | 47 | `[a-z]` | Any character between `a` and `z`, inclusive | 48 | `[^xyz]` | The opposite of `[xyz]` | 49 | `\d` | ASCII digits (0 through 9, inclusive) | 50 | `\D` | Anything except ASCII digits | 51 | `\s` | ASCII spaces (space, tab, newline, carriage return, form feed) | 52 | `\S` | Anything except ASCII spaces | 53 | `\w` | The same as `[0-9A-Za-z_]` | 54 | `\W` | Anything except the characters matched by `\w` | 55 | `[[:alnum:]]` | The same as `[0-9A-Za-z]` | 56 | `[[:alpha:]]` | The same as `[A-Za-z]` | 57 | `[[:ascii:]]` | Any ASCII character | 58 | `[[:blank:]]` | ASCII tab or space | 59 | `[[:cntrl:]]` | ASCII/Unicode control characters | 60 | `[[:digit:]]` | The same as `[0-9]` | 61 | `[[:graph:]]` | All "graphical" (printable) ASCII characters | 62 | `[[:lower:]]` | The same as `[a-z]` | 63 | `[[:print:]]` | The same as `[[:graph:]]` | 64 | `[[:punct:]]` | The same as ``[!-/:-@[-`{-~]`` | 65 | `[[:space:]]` | The same as `[\t\n\v\f\r ]` | 66 | `[[:upper:]]` | The same as `[A-Z]` | 67 | `[[:word:]]` | The same as `\w` | 68 | `[[:xdigit:]]` | The same as `[0-9A-Fa-f]` | 69 | `\pN` | Unicode character class by using single-letter class names ("N" in this example) | 70 | `\p{Greek}` | Unicode character class by unicode name ("Greek" in this example) | 71 | `\PN` | The opposite of `\pN` | 72 | `\P{Greek}` | The opposite of `\p{Greek}` | 73 | `xy` | `x` followed immediately by `y` | 74 | <code>x\|y</code> | either `x` or `y`, preferring `x` | 75 | `x*` | zero or more `x`, preferring more | 76 | `x*?` | zero or more `x`, preferring fewer | 77 | `x+` | one or more `x`, preferring more | 78 | `x+?` | one or more `x`, preferring fewer | 79 | `x?` | zero or one `x`, preferring one | 80 | `x??` | zero or one `x`, preferring zero | 81 | `x{n,m}` | between `n` and `m` repetitions of `x`, preferring more | 82 | `x{n,m}?` | between `n` and `m` repetitions of `x`, preferring fewer | 83 | `x{n,}` | at least `n` repetitions of `x`, preferring more | 84 | `x{n,}?` | at least `n` repetitions of `x`, preferring fewer | 85 | `x{n}` | exactly `n` repetitions of `x` | 86 | `(x)` | unnamed capture group for sub-pattern `x` | 87 | `(?P<name>x)` | named capture group, named `name`, for sub-pattern `x` | 88 | `(?:x)` | non-capturing sub-pattern `x` | 89 | `\*` | Literal `*` for any punctuation character `*` | 90 | `\Q...\E` | Literal `...` for any text `...` as long as it does not include literally `\E` | 91 92 In addition to the above matching operators that consume the characters they 93 match, there are some additional operators that _only_ match, but consume 94 no characters. These are "zero-width" matching operators: 95 96 | Sequence | Matches | 97 | -------- | ------------------------------------------------------------------------------------------------ | 98 | `^` | At the beginning of the given string | 99 | `$` | At the end of the given string | 100 | `\A` | At the beginning of the given string | 101 | `\z` | At the end of the given string | 102 | `\b` | At an ASCII word boundary (transition between `\w` and either `\W`, `\A` or `\z`, or vice-versa) | 103 | `\B` | Not at an ASCII word boundary | 104 105 Terraform uses the 106 [RE2](https://github.com/google/re2/wiki/Syntax) regular expression language. 107 This engine does not support all of the features found in some other regular 108 expression engines; in particular, it does not support backreferences. 109 110 ## Matching Flags 111 112 Some of the matching behaviors described above can be modified by setting 113 matching flags, activated using either the `(?flags)` operator (to activate 114 within the current sub-pattern) or the `(?flags:x)` operator (to match `x` with 115 the modified flags). Each flag is a single letter, and multiple flags can be 116 set at once by listing multiple letters in the `flags` position. 117 The available flags are listed in the table below: 118 119 | Flag | Meaning | 120 | ---- | ----------------------------------------------------------------------------------------------------------------------------------------------------------- | 121 | `i` | Case insensitive: a literal letter in the pattern matches both lowercase and uppercase versions of that letter | 122 | `m` | The `^` and `$` operators also match the beginning and end of lines within the string, marked by newline characters; behavior of `\A` and `\z` is unchanged | 123 | `s` | The `.` operator also matches newline | 124 | `U` | The meaning of presence or absense `?` after a repetition operator is inverted. For example, `x*` is interpreted like `x*?` and vice-versa. | 125 126 ## Examples 127 128 ``` 129 > regex("[a-z]+", "53453453.345345aaabbbccc23454") 130 aaabbbccc 131 132 > regex("(\\d\\d\\d\\d)-(\\d\\d)-(\\d\\d)", "2019-02-01") 133 [ 134 "2019", 135 "02", 136 "01", 137 ] 138 139 > regex("^(?:(?P<scheme>[^:/?#]+):)?(?://(?P<authority>[^/?#]*))?", "https://terraform.io/docs/") 140 { 141 "authority" = "terraform.io" 142 "scheme" = "https" 143 } 144 145 > regex("[a-z]+", "53453453.34534523454") 146 147 Error: Error in function call 148 149 Call to function "regex" failed: pattern did not match any part of the given 150 string. 151 ``` 152 153 ## Related Functions 154 155 - [`regexall`](/language/functions/regexall) searches for potentially multiple matches of a given pattern in a string. 156 - [`replace`](/language/functions/replace) replaces a substring of a string with another string, optionally matching using the same regular expression syntax as `regex`. 157 158 If Terraform already has a more specialized function to parse the syntax you 159 are trying to match, prefer to use that function instead. Regular expressions 160 can be hard to read and can obscure your intent, making a configuration harder 161 to read and understand.